Pulse-echo tracking system



3 sheets-sheet 1 R. H.` RINE-S -ECHO TRACKING SYSTEM PULSE Sept. 30,1952 Filed Nov. 29, 1946 5 Sheets-sheet 2 Fllllllllll llll R. H. RINESlllllll PULSE-ECHO TRACKING v'SYSTEM Sept. 30, 1952 Filed Nov. 29, 1946Sept. 30, 1952 I R. H. RINES 2,612,637

PULSE-ECHO TRACKING SYSTEM Filed Nov. 29, 1946 3 Shee'tS-Shet 5 VOLTAGEOUTPUT 0F TIME RETRANSNITTERS.

a l, i SIGN/us RECEIVED t 1N fzscfwen, u. (1f/ig. 5.

ourPur o'F vlneo A M P. 13o.

O 6? igc 6a I OUTPUT oF SwEEP GENERATOR, l5..

BIAS OR CUTOFF LEVEL 0F s'rRoE GENERATOR, Z9,

STRUBE TO RIGHT OUTPUT O F :l 64 sTKoBE GENERATORl 29, n l 1' d'l (F13 6,1 L-f .f.;

I a* Y? curious-M4055 msPLAY /53 l C ECHO Il STROE l I v i l rig? i 4 lI d 9. a l l EcHo mcse/isms ug 6K5 i l C RANGE-MOVING our oF ECHODECREASI NG IN RANGE-MOVING OUT OF l snes: 1o LEFT lave/zio". Robert H.@1I/zes.

Patented Sept. 30, 1952 UNITED-,STATES PATENT OFFICE Robert HarveyRines, Brookline, Mass.

Application November 29, 1946, Serial No. 713,010

and improved system of Ythe above-described character adapted for usewith unsymmetrical slope pulses that have heretofore been undesirablefor use in radio-location or radar practice.

A further object is to provide a new and improved system of theabove-described character adapted for use with any type of unsymmetricalwave-form.

Still another object is to provide a new and improved radio-locationsystem responsive to the dissymmetry of the unsymmetrical receivedpulses for automatically tracking the object from which the pulses arereceived.

Other and further objects will be explained hereinafter and will beparticularly pointed out in the appended claims.

The invention will now be more fully explained `in connection with theaccompanying drawings,

in which Fig. l is a diagrammatic view of circuits and apparatusarranged and constructed according to a preferred embodiment thereof;Fig. 2 is a similar view showing further details; and Figs.

3 to 10 are explanatory diagrams, drawn in relation to one another,diagrammatically illustrating the timing of the operation of the variousparts.

A pulse generator 4 such, for example, as a multivibrator, is showntriggering a radio-frequency transmitter 5. The transmitter 5, by way ofconductors |34, excites a dipole antenna 2 to produceultra-high-frequ'ency pulsed radio energy, say, of

`3 or 1.5 centimeters wavelength. Such an output pulse of theradio-frequency transmitter 5 may, for example, be y2 micro-secondswide, though narrower or wider pulses may be used.

In practice, the transmitted radio pulse becomes provided with anunsymmetrical-amplitude envelope, as shown at |50 in Fig. 3. This mayresult from the fact, for example, that the transmitter 5 is triggeredfrom the pulse generator through a saturated pulse transformer l. Itmay, however, be produced also by other means, as though the use ofunsymmetrical triggering pulses from the pulse generator 4, or of asquegging 22 claims. (o1. 343-13) `dyne system may be used as thereceiver.

2 or a self-generating transmitter circuit. Such dissymmetry has beendisadvantageous and even detrimental to the operation of many presentdayradio-location and similar equipments. As will hereinafter appear,however, this dissym-r metry is seized upon as an advantageous featurewith the aid of which to practice the present invention.

The radio pulses emitted from the dipole f2' may be directed by areiiector 3 upon a directive antenna system, shown as a parabolicreflector E. The parabolic reflector 6 may be rotated, as by a motor 3|,to scan the area about it; for example, in azimuth or elevation. Duringsuch scanning, the parabolic reflector 6 may direct the waves toward atarget object, say, an airplane, not shown, from which they may bereflected and scattered back toward the parabolic reflector 6 and thedipole 2. The returned pulsed-energy or radio-echo reflected signal,represented in Fig. 4 at I 28, may then be fed, by way of the conductors|34 and conductors |02, to a radio-frequency re ceiver amplifier Anywell known superhetero- One such is described in SuperheterodyneReception of Micro-Waves, Reeves and Ullrich, Electrical Communications,vol. 16, No. 2, 1937; and another, on pages 551-556 of Proceedings oftheInstitute of Radio Engineers and Waves and Electrons, 1946, vol. 34, No.8, in an article entitled Radar by Schneider. The receiver of course,will receive also some of the energy of the transmitted pulse |50, asshown at |26 in Fig. 4. Transmitter-receiver devices, not shown,commonly called T-R boxes, may be used to keep the transmitted energyout of the receiver, if

desired, during the instants of transmission, as described on pages549-551 of the said Institute of Radio' Engineers volume.

The received radio-echo pulse |28, if the original pulse |56 isunsymmetrical, will naturally also be unsymmetrical. It will berectified by a rectifier or detector to produce direct-current pulses,and then amplified in vdeo amplifiers |30, in well-known televisionfashion. Suitable apparatus for performing this vfunction may be founddescribed, for example, on page 749 of Radio Engineering, by F. E.Terman,McGraw-IIil1, 1937 horizontally-spaced, vertically-disposeddeflector plates I1 and I9 of a cathode-ray-tube oscilloscope 2|. thesweep generator|5 is fed, by way of the con- The periodically increasingvoltage ofv ductors 8 and 9 and the grounds I and I I0, be`" tween theseplates |1 and I9, to deect the elecy tron stream that passes from thecathode 60 of the oscilloscope 2| past its control-grid electrode 6| andits anode |25, finally to impinge on its fluorescent viewing-screenoscilloscope face 21. The saw-tooth charging sweep voltage correspondingto thev output of the sweeplgenerator I5 thus produced between theplates I1'and I9 is represented at 62 in Fig. 6. It becomes convertedinto a horizontal line or trace of illumination 63 on the screen `21,representing -a horizontalsweep-time base.

The grid electrode 6I is normally so `biased negatively with respect tothe cathode 60 by, say, 'a'battery 'I 2|, as to permit the electronstream to produce a desired: intensity of illumination uponthe'oscilloscope face 21. A .B-battery |t|9 may constitute a source ofsupply between the cathode 60' and the anode |25.

The voltage of the video circuit `amplifiers |30 is fed to thevertically-spaced, yhorizontally'- disposed deector plates 23,125 of theroscilloscope 2| by way of conductors |04 and |05 andv grounds I3. andI8.

The saw-tooth outputvoltage 6.2 of the horizontal-sweep generatorl |5'isfed also, by rway of the conductors 8 and 9 and conductors |31, to-between the grid 30 and the cathode 32 yof the generating tube 34 oi avariable-phase voscillator or strobe-generator 29. The strobe-generator29 becomes thus triggered'to producepulsesas hereinafter described, inany desired phase .relationship with respect to the start of the `sweepvoltage 62. v f

The strobe-generator 29 is provided with a strobe or range-controlpotentiometer 40, ad-

justable by means of a slider 38. Depending on the adjustment of theslider 3 8 on the potentiometer 40, the bias of the tube 34 iscontrolled in such manner that the 'tube 34 will start to con-`condenser-resistor circuit C---R and the differentiated output is passedthrough a rectifier 4| to'select the initial differentiated signaloccurring upon conduction of the tube 34.

The output'of the strobe generator 2'9 becomes thus reduced to a shortnegative pulse |54,v as shown in Fig. 7, occurring at the instant oftime,

relative tothe start of the sweep 62, `predetermined by the biasstrobe-control setting. of the slider 38. Further ampliers, not shownmaybe used,v as Well known in the art, to make the "pulse 64 square. Othertypes of strobe generators or variable-phase multivibrators, used widelyin the radar art, may, of course, be used similarly to the generator 29.

Since the strobe generator 29 produces a pulse output 64 at a time,along the sweep voltage 62 and, therefore, along the sweep-time base 63,that depends on the setting of the bias-strobecontrol slider 38, thereading on the potentiometer-scale 43 will be a measure of thetimebetween the start of thesweep time base 63 andthe occurrence of thepulse 64. The strobe pulse 64 may be of the same width as thetransmitted radio pulse |50, or it may be slightly shorter or wider,depending on the values of the resistance of the resistor R and thecapacitance of the diierentiating capacitor C.

At the instant that the radio pulse |50 is transmitted from the dipoleantenna 2 to the distant y object, thetube, not shown, of the sweepgener- I 28 received by the dipole 2, after rectification by therectifier and amplification by the amplifier |30, is fed to the'vertically-spaced horizontallydisposed' defl'ector plates 23 and 25,thesweeptime base 63 on the face 2.1 off the cathode-ray tube 2|` isdeflected. vertically, as a vertical pulse |29, `shown. occurring' at adistance 'r' from the 'startof thesweep-time base v63 in Figs. 1, 2` and8. As the' distance r' depends lupon the: time from the start of thesweep B3 to the time of receipt of the echo,.it constitutes. a measureofthe range v'vofv the object, not shown. Actually, 41" is the-range rless a constant, namely the pulse Width of the transmitted pulse, sothat 1" dsa measure of the range r. vFrom a practical point of view,since the pulse width is very -small,v and r are essentially identicaLatleast to within the limits needed for even the most stringent ,ofradio-location purposes.

The' pulse output 64 ofthe strobe generator 29 y is fed along two paths:first, .by Way of conductors |03, to between the4 grid 6| and thecathode 60 of the cathode-ray tube 2|, in order to accelerate moreelectrons, and thus'to brighten the-sweepvtime base 63 in the region orvat the timel of the sweep that the pulse V64 occurs; and secondly, byconductors I0|, to open up a normally-nonconducting gate tube I4. y Y

With regard to the rst of these pathssince the control electrode `6| ofthe cathode-ray tube 2.| is biased negatively with respect to thecathode 60, the horizontal-sweep-time base 63 may not be very brightonthe oscilloscope face 21. Upon the arrival from the strobe generator 29,by wayof the conductors |03, however, of a brightening pulse 64'betweenthe grid 6I and the cathode 60, the cathode becomes rendered negativewith respect to the control grid 6|. The electrons emitted from thecathode 60 become thereupon accelerated, in the formof an increasedstream, l

past the control grid 6| andthe anode |25 of the oscilloscope 2|, 'toimpinge nally on the uorescent oscilloscope face 21. A selected part of`the sweep-time base 63, starting with a point alongl the sweep-time base63 corresponding to the start of the pulse B4, will thereuponbecome'brightened during the duration of the pulse 64. If the strobesetting of the slider 38 on the potentiometer 49 causes the pulse 64 tooccur at adistance r along the sweep voltage 62 or the sweep-time base63, then a portion of the time base 63 Will be brightened, starting witha point at the distance r' from the start of the timebase for a portionequal in length along the time base 63 to the pulse Width of the pulse64'.

Feeding the pulse 64 of the strobe generator 29 along the second pathbefore mentioned, by Way of the conductors to the normally positivelybiased cathode I2 of the normally non-conducting and normallyineffective voltage-responsivegate tube I4 will tend to overcome thecathode bias of a battery 6l, thereby tending to render the gate tube 4conducting. The control grid I5 of the gate tube I4 is negatively biasedby a battery 24. Rectied echo pulses fed from the receiver II to thevideo amplifiers |30 are conveyed by conductors IM, 22 and |05, througha ground 20 and the ground I8, to the control grid IB of the gate tubeI4. If Van echo pulse |28 should return at the time that thestrobe-pulsesetting of the slider 38 lcauses the pulse 94 to commence, therefore, itwill arrive to overcome the grid bias ofthe battery 24 at a time whenthe negative strobe pulse 6d is being applied to the cathode I2 toovercome the bias of this cathode` I2. The time and phase ofthe strobepulse and the echo pulse Will then coincide. The positive and negativebiases produced `by the batteries 6l and 2d upon the cathode I2 and thegrid I6 Will thus both be overcome, and the normally ineffective gatetube III will then open up and become effective to provide a pulseoutput. The pulse-output voltage of the gate tube I4, the same asappears represented at |29 in Fig. 8, centered in the strobe, appears inFigs. l and 2 as a brightened section of the sweep-time base 63 on thescreen 21 of the cathode-ray tube 2| If, therefore, the strobe settingof the slider 38 is adjusted so that part of the sweep is brightenedWhere an echo |29 is, occurring afterreection from an object, not shown,at a range r, then the echo |29 will be brightened as shown by the heavylines in Fig. 8, and the setting of the slider 38 on the potentiometer40, as read on the scale 43, will be a measure of the said range r.Strictly, as before explained, the reading Will be 1' less the constantdistance corresponding to the short pulse Width of the vtransmittedradio pulse.

For explanatory purposes, the unsymmetrical pulse |29 may be regarded asconstituted of two adjacent voltage wave-forms. As shown in Fig. 8, forexample, one of these two Wave-forms may be a square or rectangular Waveshape, indicated by the steeply rising leading edge a and a steepdotted-line falling edge c, and the other an adjacently-disposedtriangular or saw-tooth Wave shape, indicated by the steep dotted-linerising edge c and the more gradually sloping, trailing or falling edgeb. As will hereinafter be explained, depending upon` whether the targetobject, not shown, that is being tracked by the radio-location stationis receding from or approaching toward the station, the output of thegate tube id Will be substantially either a rectangular wave or aSavvtooth wave.

Any periodic voltage Wave of any shape may be regarded, according toFourier analysis, as constituted of an infinite number ofdifferent-frequencied periodic voltage-wave components of diierentamplitudes. A periodic square-wave or `6' rectangular-Wave voltage maytherefore be obtained by adding a very large number ofdifferentfrequencied voltage signals. A symmetrical time periodicsquare-Wave or rectangular-Wave Voltage EUS), of unity amplitude andfundamental "frequency f, Where t is the time, may be represented by thesummation expression:

Sin 21r5 ft Sin 27s-nfl:

5ml T) This wave form is constituted of the fundamental frequencyf andall its odd multiples, namely, the third harmonic 3f, the fth harmonic5f, and so on to the nth odd harmonic, nf. The corresponding symmetricalperiodic saW-tooth-voltage Wave, E t), of unity amplitude andfundamental frequency f, is constituted, in addition to the frequenciescomprising the square-Wave voltage, of even-harmonic-frequencycomponents 2f, 4f, etc.:

In both cases, the amplitudes of the harmonic are inversely proportionalto the frequency, though the amplitudes cf those of the frequencycomponents common to the two Waves are not numerically the same. f

In the case of non-symmetrical time-periodic rectangular-Wave andsaW-tooth-Wave voltages, furthermore, the amplitudes of thosefrequencies that are common to the two voltage signals are not the samein the two Waves. The amplitude Cn of each nth harmonic-frequencycomponent present in the unsyinmetrical square or rectangular Wave, asthe wave a, c of Figs. 8 and 9, occurring once ever T seconds, andyhaving a peak amplitude A, and a time duration or Width d, may berepresented by:

2A (fn-mr sln T The` amplitude Cn of the nth harmonic-frequencycomponent present in anvunsymmetrical saW-tooth-Wave voltage, such as c,b of Figs. 8 and l0 is represented by- Where d is the width of thesaw-tooth Wave.

It is therefore possible to discriminate between voltage signals ofrectangular and saw-tooth- Wave-amplitucle envelopes either by selectingfrequency components present in one and not in the other, or by makinguse of the fact that the amplitudes of those frequencies in common tothe Waves are diierent.

|4, ywhen it conducts, is fed to'two further amplifiers Wand 'I'heamplier 58 is shown feeding aV coil 53 of a differential meter 54, andthe amplifier 5| an opposing coil 52. A. meter needle 55,. .responsiveto the fields yproduced by the two opposing coils .52 and 53, willremain .in a neutral or null position if the outputs of the twoamplifiers 50 and 5| are equal.

The amplifier 5| may be tuned to certain frequencies of a saw-tooth wavethat are dissimilar to or not present in a square wave, and theamplifier 58 may be tuned to certain squarewave-frequency components. Inthat event, if

common square-wave and saw-tooth frequencies 'are dissimilar,v theamplifier '59 shall give the greater output if a square wave is present,and the amplifier 5| shall give the greater output if va saw-tooth waveis present. Either the lowerfrequency components or the higher-videocomponents of the waves may be used. The plurality of amplifiers 50 and5|, each selectively and discriminatively responsiveto one or more ofthe frequency components of square or saw-tooth XX waves'and to the"distinctive amplitudes of these components, may obviously also besupplemented with further filtering networks, as is well known in theamplifier art.

When an operator has detected, on the oscilloscope face 21,` a. targetobject appearing as a deiiection |29 on the sweep-time base 63, he may'adjust the variable-phase strobe-control slider l 38 to the properposition on the potentiometer 4|! so as to aline the forward edge of thebrightening section with the deflection |29, as illustrated byFig. 8.Once the strobe pulse 64 has thus justment of the slider 38 to theproper position on the potentiometer 48, thegate tube I4 will open up,as previously described, to give a pulse output of the shape of thepulse |29 in Fig. 8. The amplifiers 58 and 5I, fed with. the combinationof the square Wave and the saw-tooth wave making up the unsymmetricalpulse |29, are adjusted to give equal outputs, in order that the meterneedle. 55 shall occupy the neutral or null position. The strobe orlengthened section of the sweep is then on target. The echo |29 may nowbe automatically followed or tracked constantly on the oscilloscope face21 as the target, not shown, from which the radio waves are reiiected,moves with respect to the radio-location station. There will thus bemade available automatically, ,at the strobe-potentiometer-system'slider 38, continuous-range readings that could be used for predictionand gun-directing purposes.

If the target, not shown, as represented by the ech-o |29, is increasingin range, the echo |29 will move out of the brightened strobe sectionof'. the sweep-time base 63, toward the right, as

YYthe output 0f Vthe gate tube I4 contains certain 1 been adjusted so asto produce a brightened section or strobed'region of the sweep-time base63 centered on the echo |29, Fig. 8, by the ad- .ent the strobe.

tubeV |4, vat this time, v'contains onlythe ldistinctive frequencycomponents of the square wave, as. previously explained, thesaW-tooth-wav'ecomponents being lost, since the portion c, o is lostoutside the strobe, the amplifier 158 will have a greater output `thanthe amplifier 5|, causingthe meter needle 55 to swing to theleft,.towardsthe plus` position. The .field coil cfa motor 56fwiil1thereupon become connected 'into circuit, witlra polarity suchthatiitsscreW-shaft shallrevolve Yin La.. direction such as to move Ytheslider. 38, say, Y up onthe potentiometerl 481, 'thereby increasingthebias on the strobe-generator tube. 34.

With increasing bias, the strobe. tube 34 will begin towconduct at alater time or phase than, for example, the instant along the sweepvoltage 6.21 indicated at 68, Fig. 6. The brightening strobe section vwill .therefore move out toward the right, until the strobe again coversthe 'echo |`29to reproduce the on-target condition of Fig. 81. Theftube50fand`lthe tube 5|,wil1 then again 'have equal outputs, and the needle55 willagain'assume the neutral or nullv position. The new position ofthe slider 38 will then indicate the new range r of the target, notshown, from which the radio echo |-29;is now being received.

If, on the other hand, the target is decreasing in range, the echo I 29will moveout of the-strobe or brightened vportieri of Vthe' sweep-timebase 63, towardthe left, as shown in Fig. 10. Only the saw-tooth part orportion c, bof the echo |29 will then be inthe strobe section. Theoutput of the gate tube |4 will thus contain thesawtooth-voltage-component frequencies, with their respectiveamplitudes, the square-wave compo'- nents nowfbeing lost, since-theportion a, cVi's lost outside the strobe. Thisresults in a greateroutput inthe ampliiier 5| than in the ampliiier field coil of themotor.56 so as to cause the motor 5G to turn in the opposite direction.`The motor shaft 51 will then'turn in the direction oppositeito thatpreviously described, eiecting,'say, a lowering of the slider 38 onthe'potentiometer '40, and decreasing the` bias .on the strobe-generatortube 34.

With this decrease in the bias orcut-oif Vof the tube 34, the tube will,conduct at a time earlier than is indicated, for example, by the point68 along the. sweep voltage 62, Fig'. 6. The strobe or brighteningsection will thus move in, in range or distance, :on the sweep 63, withthe echo |28, until it will again cover the echo |29, similar to thecondition represented in Fig. 8. The meter needle 55 will again assumethe neutral or null position, and the new position of the slider 38willindicate the new range 1 of the target object. The strobe control isthus moved automatically with increasing or decreasing range 1' of thetar'- get being tracked by the radio-location station, to yieldautomatic and continuous readingsof this range r. It is thereforepossible automatically to follow the range T of the unsymmetricalradio-echo signal from the distant object, not shown. In each case, avariable-phase signal or impulse-voltage wave 64 is superimposed, in thetube I4 and on the cathode-ray tube 21|, on the unsymmetrical amplitudeenvelope reference echo signal constituted of the impulse-voltage wave|29.y Any change in relative-phase relationship, as the echosignalattempts to move out of 9 super-position or coincidence with thevariablephase signal, will result in producing further voltage outputsof the tube it, containing distinctive voltage signals `from eitherpredominantly square-Wave or saW-tooth-Wave components, depending uponthe direction in which the echo signal is moving. These furthervoltages, produced in response to the departure from the superpositionof the variable-phase and the reference-echo signal, as a result of thedissymetry of the received echo signal, operate t modify the phasev ofthe superimposing voltage signal, thereby to restore the variable-phasesignal back into superposition or coincidence with the superimposedecho-voltage signal. The variable-phase `and echo-reference signalvoltages are` thus always maintained automatically synchronized, tofollow, automatically the range 1- of the `radioecho signal 129 of thedistant object, not shown.

The invention has been described in connection with the use of anunsymmetrical voltage signal having a signal envelope comprising, inpart, a steeply rising portion a and, in part, a more gradual fallingportion b, and `upon which a variable-phase voltage signal Yissuperimposed suoli that, when the steeply rising portion a or thegradual falling portion b of the unsymmetrical voltage signal envelopefalls out of superposition with the variable-phase voltage signal 29,further voltages are produced to modify the phase of the variable-phasevoltage signal, thereby to bring said signal back into superpositionWith the unsymmetrical signal. The invention is not, however, limited tothe use of the described signal, `but is `operable with any other typeof unsymmetrical voltage pulses where, for example, frequency oramplitude diiferentiationl can be made between the various `parts of theunsymmetrical voltage wave. Further modications will also occur topersons skilled in the art,y and all such are considered toV fall Withinthe spirit and the scope of the invention, as 4dened in the appendedclaims.

What is claimed is: n

l. A radio-location-ranging system having, in combination, means forreceiving radio-Wave signals from a movingvobject, said signals havingunsymmetrical rising and falling portions, means cooperative with thereceiving means for. indicating the range of the object, and meansselectively responsive to the dissimilar characteristics of the risingand falling portions ofthe radio-wave signals for automaticallycontrolling the indicating means-to provide continuous and automaticreadings ofthe range of the object.

2. A radio-location system having, incombination, means for receivingradio signals from an object, said signals having portions ofunsymmetrical characteristics, cathode-ray-tube means for displaying thereceived signals, means for producing a variable-phase signal and forsuperimposing it on the displayed signals, means -for indicating when adisplayed signal starts to move out of superposition with thevariable-phase signal and the direction in Which it starts to move, andmeans cooperative with the indicating means and selectively responsivetothe characteristic of that portion of the displayed signal stillsuperposed by the variable-phase signal dissimilar to the characteristicof the portion of the signal out of superposition for automaticallyvarying the from a `moving object, said pulses having an rivelope thatsteeply rises and then more gradually falls, and means cooperative withthe receiving means andselectively responsive to the steeply rising andgradually falling characteristics of the pulse envelopegforautomatically tracking the range oftheobjectrin its movement. y

Ll. A radio-location system having, in combination, means forreceivingradio-impulse signals having la signalV envelope comprising a steeplyrising portion and a more gradually falling portion, means, for`producing variable-phasevoltage signals, means for causing thevariablephase-voltage signals and the radio-impulse signals to coincidein time and phase relationship, meanscooperativevvith the last-namedmeans for indicating when the radio-impulsesignals andvariable-phase-voltage signalshave changed their time and phasecoincidence and Whether the change isinthe directionrunning from thesteep rising portion to the gradually falling portion of the envelope ofthe impulse signals or in phase of the variable-phase signal, thereby tonation, means for receiving pulses of radio Waves Y the oppositedirection, and means selectively responsive to the steeply rising andgradually falling characteristics of the radio-impulse signals asindicated by thelast-named means and cooperative `with thevariable-phase voltagesignal-producing means for restoring the phase andtime coincidence of the radio-impulse signals and thevariable-phase-voltage signals.

5. A radio-location-ranging system having, in combination, means forreceiving from a moving object radio-Wave signals having a` signalenvelope comprising fa rising portion having substantially thecharacteristics of a square or rectangular-wave voltage signal and a`falling portion having substantially thecharacteristics of a triangularor saW-tooth-Wave voltage signal, and means cooperative Witnthereceivingmeans and selectively responsive to the rising and falling portions ofthe radio-signal envelopes for automatically tracking the range'of theobject.

6. A signal-control system havingin combination, means for producing avoltage signal comprising a plurality of portions each 'havingdistinctivefrequency components one or'more of .which may become lost, aplurality of means each selectively responsive Vto one or more of thedistinctive frequency components, means for indicating the presence orabsence in thevoltage signal of certain of the distinctive frequencycomponents of corresponding portionsof the voltage signal, and meansresponsive to the indicating means for restoring to thevoltage signalthe lost distinctive frequency component or components.

'LA signal-control systemv having, in combination, meansA for producinga voltage signal comprising aplurality of portions each having frequencycomponents of distinctivevoltage amplitudes one or more of whichfrequency components may become lost, a plurality of means eachselectively/,responsive to one or more of the frequency components andto their respective distinctive voltage amplitudes, means for indicatingthe presence or absence in the voltage signal of certain of thefrequency components of distinctive amplitude, and means responsive tothe indicating means `forfrestoring to the voltage signal the lostfrequencycomponent or components of distinctive amplitude or amplitudes.

8. A radio-location-ranging system having, in combination, means forreceiving from a moving object radio-Wave signals having a Waveformcomprising two portions of different shape, means for producing avariable-phase signal and 1-1 'for vsuperiinposi-n'g it upon a `receivedsignal to indicate the range of the object, means forproduci-ng afurther voltage signal having 'substantially the shape of one-of theportions of the radio-Wave signal in response to a departure'in onedirection from the superposition vof the radiowave. signal and thevariable-'pha'sev signaland for producing stilla further voltage signalhaving substantially the shape of the other portion of thetvvo portionsof the-adio-Wave `'Signal in vresponse to -a departure intheopposite-direction from the superposition ofthe radio-wave 'signal vandthe variable-phase signal, and means selectively responsive to thedieren't shape characteristics of the further voltage signals 'forre-'storing the superposition ofthe radio-Wave signal `'and thevariable-phase signal, therebycontinu'o-uslyv to indicate therange ofthe moving object. y 'y Y u Y 9. A radiolocation-ranging-'system having,in combination;- ineans for receiving from la moving object radio-Wave"signals having a wave-form ycoinpr-ij'si-n'gy a 'steeply-rising portionand a more gradually vfalling portion, means for producing avariable-'phase signa-1 vand 'for superimposing it ui'onfa receivedsignal toin'dic'a'te the range of tholoject, means 'for -poducing asteeply-rising fi'itlierlvoltage-signalin response to a departure ih'one direction '(frin the-superposition of the radio-Wave sign-al and'the variable-phase signal ancrer 'producing a mores-gradually failingfurther-vonage signal Pinrespense to a departure in the opposite direct'n `froirn the superposition of che radio-wave signal and the` variable-'phas'e signal, and lmeansselectively responsive 'to the steeply-risingE and gradually falling characteristics of the further voltage signals'for restoring the 'superposition o'f the radio-Wave signal and thevariable-phase si'g'nalf, thereby continuously 'to-'indicate therange-of the moving ob- 10. A radio-looation-'ianging v'syst'ernhaving,in combination, means for'receiving from 'a moving 'object radio-Wave`signal'sliaving portionsof u'nsymmetricai frequency-componentcharacteristics, means for producing a variable-phase signal andfor'superimposingit upon Va received signal to indicate the range 'of `theobject, 'means 'for producinga further 'voltage signal :having all ofthe frequency components of the radio-wave signal, means for varying thefurther 'voltage signal in response tors, departure from ycomplete'superposition of the lu'ns-'ymm'et'ri'c'al radio-Wave nation, means forAreceiving pulses 4of -radio Waves from aymoving object, said pulsesfhfaving yan envelope the lrisingfand. -falflingportions'of which areunsymmetrical.'means cooperative with fthe receiving means controlled in:accordance with the range of the object, and means-selectivelyresponsive to the dissimiiarcharacteristics of the risi-ng-vand falling portionsof the .-pulse envelope for #controlling thesecond-named means 'automatimeans' automatically to determine 'the rangeof mecbgect. y

13-. A radiolocation-ranging' system having, in combination, means forreceiving `from an object pulses of radio waves having an ('e'riveicp'ethe risingand 'fallingportions of which have common `frequency,components of differing amplitudes, means cooperative with the receivingmeans controlled in'a'coorda'nce with the range of the object,

and means-selectively 'responsive to the said differing amplitudes ofthecommon frequencycomponentes-inthe rising and falling portions of the'pulseenvelop'e for controlling the second-named means automatically todetermine the range 'of the object.

:1"4. AYradio-location-ranging system having, in combination, means forreceiving from an object pulses of lradio Waveshaving anenvelope therising and falling portions of which have diifering frequencycomponents, means cooperative With the receiving means controlled inaccordance with the range of the object, vand means selectively.responsive 'to' the differing Ifrequency components in the risingy andfalling portions of the pulse envelope for controlling the second-namedmeans automatically to Adetermine the range of the object. r Y

r11'5. electric system having, in combination, means l:for Vproducing.relatively vvarying signal voltages one of which has por-tions ofunsymmetrical characteristics, means'l'for 'superposing the signal'voltages, means for producing further voltages characteristicallydistinctive of one of thev portions of the said Aone signal 'voltage lin'response 4to a departure. from the vsuper-position of tliesignalvoltages, meansforfselectively responding tothe distinctive:characteristic of the `said further voltages, 'and means controlled byA`the yselectively responding means for restoring the super-position ofthe signal voltages.

16'. Anfelectric `system having, in combination, means for producingIrelatively varying signal voltages one of which has portions ofdiffering frequency-component characteristics, means for `superimposingthe signal voltages, means for producingiurther voltages having at leastonefrev quency component distinctive lof one portion of the said onesignal voltage 'in response to a 'depa'rture from thesuperpositionfofthe v'signal voltages, means for selectively responding to thevdistinctive frequency component, and mea-ns controlled by4 theselectively responding means 'for restoring tne'superposition lof thesignal voltages. l'l. An electric system having, in combination,

means :for producing relatively varying signal or impulse voltages oneof vwh-ich has portions of unsymmetrica-l characteristics, means -forsuperrimposing. the signal `or impulse voltages, means -for yproducingfurther voltages"characteristically distinctivef the diilei'ent portionsof the said one Asignal or impulse voltage 'in fi-es'pon's'e 'to -de-.parture's from the superposition of 'the signal or impulse voltages,discriminating means connected with Vthe further-voltage-producing meansfor selecting characteristics of one portion of the said one signal orimpulse voltage not present in the other portions, and means controlledby the discriminating means for restoring the superposition of thesignal or impulse voltages.

18.-A radio-location system having, in combination, means for receivingradio signals from an object having portions of differingfrequencycomponent characteristics, means for superimposing a, voltagesignal upon the received signal, means for producing further voltageshaving at least one frequency component distinctive of one portion ofthe received signal when the received signal and the voltage signal moveout of superposition, means for selectively responding to thedistinctive frequency component, and means controlled by the selectivelyresponding means for restoring the superposition of the voltage signaland the received signal.

19. An electric system having, in combination, means for producing afirst voltage signal and a second voltage signal having a plurality ofparts of different frequency-component characteristics, means forproducing further voltages when one or more of the parts of thesuperimposed second voltage signal fall out of superposition with thesuperimposing first voltage signal having at least one frequencycomponent distinctive oi the still superposed part or parts of thesecond voltage signal, means for selectively responding to thedistinctive frequency component, and means controlled by the selectivelyresponding means for modifying the phase of the superposing firstvoltage signal to bring the superposing first voltage signal back intosuperposition with the superposed second voltage signal.

20. An electric system having, in combination, means for producing avariable-phase-voltage Wave and a reference-voltage wave having portionsof unsymmetrical characteristics, means for superimposing thevariable-phase-voltage wave and the reference-voltage wave, means forproducing further voltages characteristically distinctive of one of theportions of the referencevoltage wave as the voltage waves change inrelative phase relationship, means for selectively responding to thedistinctive characteristic of the said further voltages, and meanscontrolled by the selectively responding means for bringing the phase ofthe variable-phase-voltage wave back into coincidence with the phase ofthe reference-voltage Wave.

21'.A radio-location system having, in combination, means for receivingfrom an object a radio-echo signal having portions of unsymmetricalcharacteristics, means for supelnflposq ing a voltage signal upon theecho signal, means for producing further voltage signalscharacteristically distinctive of one of the portions of the receivedecho signal when the echo signal moves out of superposition with thevoltage signal, means for selectively responding to the distinctivecharacteristic of the said further voltage signals, and means controlledby the selectively responding means for restoring theV superposition ofthe voltage and echo signals.

22.An electric system having, in combination, means for producing a rstvoltage signal and a second voltage signal having a signal envelopecomprising a, steeply rising portion and a more gradual falling portion,means for superimposing the voltage signals. means for producingvfurther voltages having the distinctive characteristics of either thesteeply rising or the gradual falling portions of the secondvoltage-signal envelope when the second voltage signal falls out ofsuperposition with the superimposing first voltage signal, meansselectively responding to the distinctive characteristics, and meanscontrolled by the selectively responding means for modifying the phaseof the first or superimposing voltage signal to bring the first voltagesignal back into superposition with the second voltage signal.

ROBERT HARVEY RINES.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,712,051 Round May 7,` 19291,987,730 Cravath Jan. 15, 1935 2,209,507 Campbell July 30, 19402,379,689 Crosby July 3, 1945 2,389,025 Campbell Nov. 131, 19452,389,948 Bartels Nov. 2.7, 1945 2,401,432 Luck 1 June 4 1946 2,412,612Godet Dec. 17, 1946 2,416,088 Deerhake Feb. 18, 1947 2,416,562Alexanderson Feb. 25, 1947 2,416,895 Bartelink Mar. 4, 1947 2,417,032Wolfi Mar. 4, 1947 2,417,248 Godet Mar. 11, 1947 2,418,143 Stodola Apr.1, 1947 2,419,567 Labin Apr. 29, 1947 2,421,020 Earp May 27, 19472,422,074 Bond June 10, 1947 2,433,667 Hollingsworth Dec. 30, 19472,467,208 Hahn Apr. 12, 1949 2,482,544 Jacobsen Sept. 20, 1949 2,495,753Mozley Jan. 31, 1950

